The long-term objective is to understand the transformation of newly encoded memories from an initial fragile state to a more stable state. The neural mechanisms responsible for this memory consolidation at the neural-systems level are essential for long-term memories. Amnesia results when consolidation is compromised. The proposal specifies a period of research training that includes the following specific aims: 1) to identify neural correlates of successful memory consolidation in humans, 2) to contrast neural correlates of memory consolidation with those of successful memory encoding, and 3) to identify changes in retrieval that occur as memories progress through the consolidation process. Scalp EEG will be recorded from human subjects as they encode 200 word pairs. For a subset of the word pairs, memories will be reactivated when subjects see the first word from the pair. One week later, memory is expressed when subjects view a word from one pair and attempt to retrieve the associated word. It is posited that consolidation will occur during the period directly after this reactivation, and that EEG measures will be sensitive to this processing. Testing after a 1-week delay will be used to show that reactivation leads to superior retrieval, representing a beneficial effect of reactivation. In addition, EEG responses during reactivation will be analyzed in the time and frequency domains. A comparison based on retrieval success on the test day will reveal neural correlates of successful consolidation. These results will be compared with a similar contrast of EEG responses at initial encoding as a function of later retrieval success. A third contrast will compare involve repeated presentations of a word at multiple stages as memories progress through the consolidation process. Public health Relevance: This research will help reveal brain processes that allow humans to form long-lasting memories. Understanding these processes will shed light on various disorders of memory in neurological and psychiatric disease, including individuals who cannot recall events from the past and individuals whose memories for traumatic past events have profound negative consequences.